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  • Saving tree-structures in Databases

    - by Nina Null
    Hello everyone. I use Hibernate/Spring and a MySQL Database for my data management. Currently I display a tree-structure in a JTable. A tree can have several branches, in turn a branch can have several branches (up to nine levels) again, or having leaves. Lately I have performanceproblemes, as soon as I want to create new branches on deeper levels. At this time a branch has a foreign key to its parent. The domainobject has access to its parent by calling getParent(), which returns the parent-branch. The deeper the level, the longer it takes to create a new branch. Microbenchmark results for creating a new branch are like: Level 1: 32 ms. Level 3: 80 ms. Level 9: 232 ms. Obviously the level (which means the number of parents) is responsible for this. So I wanted to ask, if there are any appendages to work around this kind of problem. I don’t understand why Hibernate needs to know about the whole object tree (all parents until the root) while creating a new branch. But as far as I know this can be the only reason for the delay while creating a new branch, because a branch doesn’t have any other relations to any other objects. I would be very thankful for any workarounds or suggestions. greets, jambusa

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  • Public static variables and Android activity life cycle management

    - by jsstp24n5
    According to the documentation the Android OS can kill the activity at the rear of the backstack. So, say for example I have an app and open the Main Activity (let's call it Activity A). In this public activity class I declare and initialize a public static variable (let's call it "foo"). In Activity A's onCreate() method I then change the value of "foo." From Activity A the user starts another activity within my app called Activity B. Variable "foo" is used in Activity B. Activity B is then paused after the user navigates to some other activities in other apps. Eventually, after a memory shortage occurs, Activity A then Activity B can be killed. After the user navigates back to my app it restarts (actually "recreates") activity B. What happens: 1) Will variable "foo" at this point have the value that was set to it when Activity A's onCreate() method ran? 2) Variable "foo" does not exist? 3) Variable "foo" exists and but is now the initialized value and not the value set in Activity A's onCreate() method?

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  • Why is my panel not positioned correctly even after setting the boundaries?

    - by nutellafella
    I'm trying to make a simple GUI with radio buttons and I grouped them into one panel. I wanted it positioned on the leftmost side so I used the setBounds method. Whatever numbers I put on the parameters, the panel won't move. Are panels not affected by the setBounds method? Or is there another way to position my panel. Here's the snippet of my code: JPanel radioPanel = new JPanel(); radioPanel.setLayout(new GridLayout(3,1)); JRadioButton Rbutton1 = new JRadioButton("Credit Card"); JRadioButton Rbutton2 = new JRadioButton("E-Funds"); JRadioButton Rbutton3 = new JRadioButton("Check"); Rbutton3.setSelected(true); ButtonGroup Bgroup = new ButtonGroup(); Bgroup.add(Rbutton1); Bgroup.add(Rbutton2); Bgroup.add(Rbutton3); radioPanel.add(Rbutton1); radioPanel.add(Rbutton2); radioPanel.add(Rbutton3); radioPanel.setBounds(10,50,50,40); //this is where I'm trying to position the panel with the radio buttons paymentPanel.add(radioPanel); contentPane.add(paymentPanel); //contentPane is the frame contentPane.setVisible(true);

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  • setting user.dir system property in JBoss 5.1

    - by Spiderman
    In JBoss 4.2.3 the System property 'user.dir' is defined to be <JBoss-root>/bin when I ran the same application on JBoss 5.1 I noticed that it cannot find the System property user.dir why there is no default definition for version 5.1? and how can I define it manually? I followed this suggestion and added my property into properties-service.xml but it had no affect and still JBoss couldn't find the system:user.dir value.

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  • Remove duplicates from a list

    - by Mercer
    Hello i want to remove duplicates from a list i do this but not working List<Customer> listCustomer = new ArrayList<Customer>(); for (Customer customer: tmpListCustomer) { if (!listCustomer.contains(customer)) { listCustomer.add(customer); } }

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  • Simple but good pattern for EJB

    - by Sara
    What would you suggest as a good and practical but simple pattern for a soloution with: HTML + JSP (as a view/presentation) SERVLETS (controller, request, session-handling) EJB (persistence, businesslogic) MySQL DB And is it necessary to use an own layer of DAO for persistence? I use JPA to persist objects to my DB. Should I withdraw business logic from my EJB? Sources online all tell me different things and confuses me...

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  • How to preserve object identity across different VMs

    - by wheleph
    To be specific let me illustrate the question with Spring http-remoting example. Suppose we have such implementation of a simple interface: public SearchServiceImpl implements SearchService { public SearchJdo processSearch(SearchJdo search) { search.name = "a funky name"; return search; } } SearchJdo is itself a simple POJO. Now when we call the method from a client through http-remoting we'll get: public class HTTPClient { public static void main(final String[] arguments) { final ApplicationContext context = new ClassPathXmlApplicationContext( "spring-http-client-config.xml"); final SearchService searchService = (SearchService) context.getBean("searchService"); SearchJdo search = new SearchJdo(); search.name = "myName"; // this method actually returns the same object it gets as an argument SearchJdo search2 = searchService.processSearch(search); System.out.println(search == search2); // prints "false" } } The problem is that the search objects are different because of serializaton although from logical prospective they are the same. The question is whether there are some technique that allows to support or emulate object identity across VMs.

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  • Where about should my main class be created in a project?

    - by Dan
    The problem is where a class should be created in my code. An example is I have a UI class and a main logic class that controls other objects. Should the main logic class create the UI object, or should the UI object create the instance of the main logic class? An explanation of which method is best and why would be ideal. Thanks.

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  • Handling multiple exceptions

    - by the-banana-king
    Hi there, I have written a class which loads configuration objects of my application and keeps track of them so that I can easily write out changes or reload the whole configuration at once with a single method call. However, each configuration object might potentially throw an exception when doing IO, yet I do not want those errors to cancel the overall process so that the other objects are still given a chance to reload/write. Therefore I collect all exceptions which are thrown while iterating over the objects and store them in a super-exception, which is thrown after the loop, since each exception must still be handled and someone has to be notified of what exactly went wrong. However, that approach looks a bit odd to me. Someone out there with a cleaner solution? Here is some code of the mentioned class: public synchronized void store() throws MultipleCauseException { MultipleCauseException me = new MultipleCauseException("unable to store some resources"); for(Resource resource : this.resources.values()) { try { resource.store(); } catch(StoreException e) { me.addCause(e); } } if(me.hasCauses()) throw me; }

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  • How to get the EJB listening port?

    - by Alotor
    I'm currently developing a library for monitoring calls to several remote services (WebServices, EJBs...). One of the parameters that i would like to register is the port from which a EJB is called (a Stateless Session Bean invoked like a remote object) There is any standarised way of getting the port? Or should I inspect the JNDI tree for this kind of information? I'm using the EJB 2.1 spec, but it's also posible for me to use EJB 3

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  • Exception handling protocol for methods

    - by athena
    Is there any specific protocol for handling exceptions in public methods? Consider this eg. public int someMethod() { try{ code that might throw an exception } catch(Exception e) { log the exception } } Say that this method might throw an ArrayIndexOutOfBoundsException. So, is it correct to handle this Exception in the method itself (as in the example) or throw it and assume that the calling method will handle the Exception?

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  • How to draw on JPanel on fixed position?

    - by kovike
    I have JPanel wrapped in JScrollPane and I want the rectangle to be drawn always on the same position = moving with scrollbars wont affect the visibility of the rectangle. I tried following code: public void paintComponent(Graphics g) { g.setColor(Color.red); g.drawRect(50, (int)getVisibleRect().getY(), 20 , 20); } but it only repaints the rectangle when size of whole JPanel is changed.

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  • How to create Chat application using Servlets & JSP

    - by Crazy boy
    I want to create chat application using Servlets & JSP. May I know how can I create chat application as I have never created before? How much knowledge I need to have to create chat application? Is there any need of networking API to create chat application? What's the design pattern I need to follow to create that application? Is there any need of database?

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  • How to change internal buffer size of DataInputStream

    - by Gaks
    I'm using this kind of code for my TCP/IP connection: sock = new Socket(host, port); sock.setKeepAlive(true); din = new DataInputStream(sock.getInputStream()); dout = new DataOutputStream(sock.getOutputStream()); Then, in separate thread I'm checking din.available() bytes to see if there are some incoming packets to read. The problem is, that if a packet bigger than 2048 bytes arrives, the din.available() returns 2048 anyway. Just like there was a 2048 internal buffer. I can't read those 2048 bytes when I know it's not the full packet my application is waiting for. If I don't read it however - it'll all stuck at 2048 bytes and never receive more. Can I enlarge the buffer size of DataInputStream somehow? Socket receive buffer is 16384 as returned by sock.getReceiveBufferSize() so it's not the socket limiting me to 2048 bytes. If there is no way to increase the DataInputStream buffer size - I guess the only way is to declare my own buffer and read everything from DataInputStream to that buffer? Regards

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  • Extracting rightmost N bits of an integer

    - by srandpersonia
    In the yester Code Jam Qualification round http://code.google.com/codejam/contest/dashboard?c=433101#s=a&a=0 , there was a problem called Snapper Chain. From the contest analysis I came to know the problem requires bit twiddling stuff like extracting the rightmost N bits of an integer and checking if they all are 1. I saw a contestant's(Eireksten) code which performed the said operation like below: (((K&(1<<N)-1))==(1<<N)-1) I couldn't understand how this works. What is the use of -1 there in the comparison?. If somebody can explain this, it would be very much useful for us rookies. Also, Any tips on identifying this sort of problems would be much appreciated. I used a naive algorithm to solve this problem and ended up solving only the smaller data set.(It took heck of a time to compile the larger data set which is required to be submitted within 8 minutes.). Thanks in advance.

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  • How to find which file is open in eclipse editor without using IEditorPart?

    - by Destructor
    I want to know which file (or even project is enough) is opened in eclipse editor? I know we can do this once we get IEditorPart from doSetInput method, IFile file = ((IFileEditorInput) iEditorPart).getFile(); But I want the name of file without using IEditorPart, how can I do the same? Checking which is the selected file in project explorer is not of much help because, user can select multiple files at once and open all simultaneously and I did not way to distinguish which file opened at what time. Adding more info: I have an editor specified for a particular type of file, now every time it opens, during intializing editor I have some operation to do based on project properties. While initializing editor, I need the file handle (of the one which user opened/double clicked) or the corresponding project handle. I have my editor something this way: public class MyEditor extends TextEditor{ @Override protected void initializeEditor() { setSourceViewerConfiguration(new MySourceViewerConfiguration( CDTUITools.getColorManager(), store, "MyPartitions", this)); } //other required methods @Override protected void doSetInput(IEditorInput input) throws CoreException { if(input instanceof IFileEditorInput) { IFile file = ((IFileEditorInput) input).getFile(); } } } as I have done in the doSetInput() method , I want the file handle(even project handle is sufficient). But the problem is in initializeEditor() function there is no reference to editorInput, hence I am unable to get the file handle. In the source viewer configuration file, I set the code scanners and this needs some project specific information that will set the corresponding rules.

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  • JDBC call not executing

    - by dbyrne
    I am working on one of the DAOs for a medium sized web application. Unfortunately, it contains very convoluted logic, and makes hundreds of JDBC stored proc calls in loops. This is out of my control. I am working on a method inside the DAO which makes a single JDBC call. The simplified version of what this method looks like is this: DriverManager.registerDriver(new com.sybase.jdbc2.jdbc.SybDriver()); Connection con = DriverManager.getConnection((String)connectionDetails.get("DATABASE_URL") (String)connectionDetails.get("USERID"), (String)connectionDetails.get("PASSWORD")); String sqlToExecute = "{call " + STORED_PROC + "(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)}"; CallableStatement stmt = con.prepareCall(sqlToExecute); //Maybe I should try calling clearParameters here? stmt.setString(1,someData); //....Set of parameters.... if (!stmt.execute()) { //execute method never returns false } stmt.close(); Its pretty much a textbook JDBC call. All this stored proc does is insert a single row. Here is where things get crazy: This code works when you run it through a debugger line by line, but fails when you run it "full speed". Not only does it fail, but it doesn't throw any exception! The execute method always returns true. It just breezes right through the JDBC call without inserting a row to the database. If you go through the log files, copy the stored proc call and run it manually, it works (just like it does in debug mode). Whats strange is that the rest of the DAO, with all its hundreds of looped stored proc calls, works fine. My thinking is that Connection or CallableStatement is caching some value behind the scenes that is screwing things up. Has anyone ever seen anything like this before? A JDBC call failing with no exceptions? I know it will be impossible to provide a complete solution to this without seeing the whole application, I am just looking for suggestions on possible issues to investigate.

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  • JSF actionListener is called multiple times from within HtmlTable

    - by Rose
    I have a mix of columns in my htmltable: 1 column is an actionlistener, 2 columns are actions and other columns are simple output. <h:dataTable styleClass="table" id="orderTable" value="#{table.dataModel}" var="anOrder" binding="#{table.dataTable}" rows="#{table.rows}" <an:listenerColumn backingBean="${orderEntry}" entity="${anOrder}" actionListener="closeOrder"/ <an:column label="#{msg.hdr_orderStatus}" entity="#{anOrder}" propertyName="orderStatus" / <an:actionColumn backingBean="${orderEntry}" entity="${anOrder}" action="editOrder" / <an:actionColumn backingBean="${orderEntry}" entity="${anOrder}" action="viewOrder"/ .... I'm using custom tags, but it's the same behavior if I use the default column tags. I've noticed a very strange effect: when clicking the actionlistenercolumn, the actionevent is handled 3 times. If I remove the 2 action columns then the actionevent is handled only once. The managed bean has sessionscope, bean method: public void closeOrder(ActionEvent event) { OrdersDto order; if ((order = orderRow()) == null) { return; } System.out.println("closeOrder() 1 "); orderManager.closeOrder(); System.out.println("closeOrder() 2 "); } the console prints the'debug' text 3 times.

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